Illuminated graphic button and switchpad assemblies are employed in automotive applications such as radios and environmental controls. Buttons for these assemblies often have backlit insignia which identify their particular functions. Such buttons are formed from a light-conducting material, i.e., a transparent or translucent material, which enables light to be transmitted through the button from the backside of the button to the insignia. A button and its insignia have been formed using paint and laser techniques or by injection molding. Paint and laser techniques generally involve the use of a transparent plastic substrate which may be painted white to form a white translucent layer over the substrate, and then painted black to form an opaque black covering over the substrate and, if present, the white translucent layer. The black covering is then lased away to form the insignia. The transparent nature of the substrate maximizes the transmission of light through the backlit component for night time viewing. If present, the white translucent layer contributes graphics whiteness by reflecting light, such that the insignia is more readily visible under natural lighting conditions during daylight hours. In contrast, buttons formed by liquid injection molding, or "LIM," entail the use of certain materials whose flow characteristics enable a two-shot molding process to form buttons having a light-conducting inner body and an outer opaque casing. A portion of the inner body is exposed through the casing after the molding operation, such that the casing delineates an insignia at the surface of the button.
Backlit buttons of the type described above must then be assembled in openings formed in a support panel, often referred to as a trimplate. The buttons are typically individually supported in a manner that permits their actuation within their respective openings, such that contacts located behind the buttons are closed in order to relay commands to the system controlled by the buttons. The components used to enable actuation of the buttons are typically formed separately from the buttons, necessitating their assembly with the buttons and the trim plate. To reduce complexity of the assembly process, these components are often mounted on a circuit board positioned directly behind the trimplate, on which the related circuitry is formed.
It is generally desirable to simplify and reduce the number of steps and components necessary to manufacture products, particular mass-produced products such as button and switchpad assemblies for the automotive industry. Therefore, it would be desirable if a backlit button assembly were available whose construction entailed fewer discrete components and enabled the elimination of certain assembly steps, resulting in a simplified and lower-cost assembly.